Electronic components unavoidably produce heat as a by-product in operating electronic systems. Heat is produced by active and passive electronic components in the form of dissipated power. The amount of power dissipated by an electronic component depends on the geometry and type of the electronic component. In most cases the primary source of heat is resistance which is the opposition to the passage of an electric current through conductors comprised in an electronic component. Heat is produced by resistors, non-ideal capacitors, inductors, transistors, integrated circuits and electrical conductors between such components. Heat is also produced by the substrate in integrated circuits. The heat increases the operating temperature of the electronic components and the overall temperature in the device in which the electronic components are used. An increased operating temperature reduces reliability of the device. The increased temperature also affects operating parameters of certain electronic components. Typically, the resistance of a resistor may change as a function of temperature. Also the gain of an amplifier is affected by the operating temperature. When a high-enough temperature is reached integrated circuits of the device may start to malfunction. The malfunctioning may first affect only specific types of integrated circuits so that the malfunctioning may first appear as subtle bugs in the device.
In order to protect against heating several solutions have been applied in computer and electronic systems. Previously, active water cooling has been used to cool processor boards. In current blade servers and tower servers fan trays with a plurality of fans have been used. However, such solutions are usually unavailable when the device needs to be miniaturized. Many table computers and laptop computers employ a finned heat sink which is installed on top of a microprocessor or a chipset from which heat must be dissipated. The fins achieve effective heat dissipation due to a large dissipation surface to volume ratio.
The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known mobile devices.